Lymphokine-activated killer (LAK) cell therapy has been applied clinically after the initial application carried by Dr.Rosenberg, NIH,U.S.A.However, the LAK cell therapy should be greatly improved of its clinical effects in order to be routine clinical cancer therapy. We discovered the expression of membrane lymphotoxin (mLT) on the LAK cells and established a method to make special LAK cells devoiding mLT expression. The LAK cells lacking mLT expression (mLT negative LAK cells) posess the surface expressions of many surface antigens such as CD3, CD4 and CD8, keep the LAK cell activities such as NK and LAK activities. On the other hand, it loose anti-tumor activities against many tumor cells such as HeLa cells. There should be some differences in the production cytotoxic factors and tumoricidic functions between mLT positive and negative LAK cells. To identify these, we made a cDNA-subtraction library and carried out ramdom sequencing. Homology investigation of cloned fragments enabled us to find out new clones that will be assocated with LAK cell activation. We deposited data of three new clones (LAK-1, LAK-4 and LAK-5) to the DDBJ data bank and also submitted a EST data to it.